1. Field of the Invention
The present invention relates generally to a fuser assembly including a rotatable backup member and a translatable heater member and, more particularly to a fuser assembly having a single biasing member for biasing the translatable heater member against the rotatable backup member.
2. Description of the Related Art
An image forming apparatus, such as a color printer typically includes four units associated with four colors, black, magenta, cyan, and yellow. Each unit includes a laser printhead that is used to provide a latent image on the charged surface of a photoconductive unit. The latent image on each photoconductive unit is developed with the appropriate color toner and is then transferred to either an intermediate transfer medium or directly to a media (such as paper) that travels past the photoconductive units.
The un-fused toner on the media is then fused to the media by application of heat and pressure in a fuser assembly. The fuser assembly includes a rotatable backup member and a translatable heater member disposed adjacent the rotatable backup member to form a nip through which the media passes for fusing the toner to the media.
FIG. 1 illustrates a fuser assembly 10 of the image forming apparatus according to a prior system. The fuser assembly 10 includes a rotatable backup member 12 and a translatable heater member 14 disposed adjacent the rotatable backup member 12. End frames 16 are disposed at the ends of the fuser assembly 10, only one of which is shown. The rotatable backup member 12 includes a backup roll 18 and a pivot 20 mounted within the end frames 16 for supporting the backup roll 18. The translatable heater member 14 has a heater housing 22 that extends through the end frames 16. Further, the fuser assembly 10 has a spring 24 positioned on each end frame 16 for loading the rotatable backup member 12 against the translatable heater member 14.
Due to space constraints in the image forming apparatus the spring 24, in the prior system, was relatively short with a high spring rate. The tolerance of this short spring 24 positioned on each end frame 16 accounted for 20% difference in force applied by the spring 24 positioned on end frame 16 disposed at one end of the fuser assembly 10 with respect to the force applied by the spring 24 positioned on end frame 16 disposed at the other end of the fuser assembly 10. This difference in force applied by the spring 24 resulted in an inconsistent and unequal loading of the rotatable backup member 12 against the translatable heater member 14.
Further, using two springs 24 magnifies geometrical differences between the ends of the fuser assembly 10 causing uneven loading of the rotatable backup member 12 against the translatable heater member 14. The uneven loading of the rotatable backup member 12 against the translatable heater member 14 results in several disadvantages such as treeing, worming, tail flip, and light print.
Therefore, it would be advantageous to have a fuser assembly that has the translatable heater member substantially evenly loaded against the rotatable backup member.